[GitHub] [tvm] syang-ng opened a new issue #9407: [Bug] Crash if we use the same variable in LetStmt and Select Expr

Mon, 01 Nov 2021 00:53:38 -0700 


syang-ng opened a new issue #9407:
URL: https://github.com/apache/tvm/issues/9407


   It seems that if we use the same variable `v` in both let statement and 
select expression like this, it will trigger crash:
   
   ```
   primfn(v: int32) -> () {
     let v = select(cast(bool, v), 150, 1)
     v
   }
   ```
   
   ### Expected behavior
   
   Throw exception or just build successfully.
   
   ### Actual behavior
   
   The program crashes. And I use gdb to trace this bug, it seems that `op` is 
nullptr in `arith/ir_mutator_with_analyzer.cc`.
   
   
![image](https://user-images.githubusercontent.com/25731241/139637905-9c3392d6-f113-4aae-aaef-2ce7e43342f6.png)
   
   
![image](https://user-images.githubusercontent.com/25731241/139637773-0b13d48e-df21-40a3-aa8e-e3d977b6d7bd.png)
   
   
   ### Environment
   
   Ubuntu18.04, cmake 3.18.2, llvm 12, tested on latest git 
[4087e72](https://github.com/apache/tvm/commit/4087e72b657eae484bb647cbd8ef86b9acf11748)
   
   ### Steps to reproduce
   
   Here is the 
   
   ```python
   import tvm
   from tvm import tir
   
   v = tir.Var('v', 'int32')
   s = tir.Select(tir.Cast('bool',v), 150, 1)
   let_stmt = tir.LetStmt(v, s, tir.Evaluate(v))
   f = tir.PrimFunc({v},let_stmt)
   tvm.build(f)
   ```
   


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